1. Field of the Invention
This invention relates to a system and method for monitoring output of printers and copiers, and in particular, it relates to such a system and method that can stop printing or copying when the quality of the output is not acceptable.
2. Description of Related Art
A conventional printer or copier will continue to make printed sheets until the printer or copier runs out of resources such as when the paper runs out or the toner goes too low or when the printer or copier encounters other errors such as hardware problem or paper jam. Sometimes the printer or copier may have other problems that cause low quality printouts but will not stop the printer or copier from continuing to print. For example, the toner may be low enough to give bad output (too light, blank areas, etc), or the print drum may have some foreign object to create smudges or spots or other visible problems on the printed sheets. Thus, unless an operator is physically at the printer or copier to check on the output, the printer or copier will continue to operate, resulting in many sheets of unacceptable output that have to be discarded. Sometimes, particularly in a professional print shop environment, it could happen that thousands of sheets of bad output are produced before the problem is noticed and printing is stopped. This wastes natural resources, money and time.
U.S. Pat. Appl. Pub. No. 2008/0037034 describes an image forming apparatus which “includes a unique information acquisition unit to acquire unique information unique to document data to be a print object from the document data; a storage unit to store the acquired unique information in association with the document data, and to store the unique information as reference unique information; an image forming unit to print an image based on the stored document data and the unique information associated with the document data on a same recording medium; a reading unit to read the printed unique information as unique information to be compared; and a control unit to compare the unique information to be compared with the stored reference unique information to stop printing of the document data when the control unit judges that the unique information to be compared and the stored reference unique information do not accord with each other.” (US 2008/0037034, Abstract.) In the preferred embodiment, the “unique information” is a hash value.